[Zope] LDAP UserFolder with dead slow LDAP server

Hi all, we are facing few problems with LDAP UserFolder in cases where authentication from the server takes long - even 20 seconds. For that time the thread of Zope naturlly freezes to wait for the server to return data. This is problematic since the centraliced LDAP-server will for sure return a lot of the queries in that fashion - and we really can't have the application to freeze down if X number of users try to login. Has anyone implemented anything that would come over similar problems with external authentication sources? -huima